We retrospectively reviewed 77 consecutive patients (82 hips) who underwent THA between February 1998 and July 2000. In all 82 hips, cemented THA was performed using a polyethylene-backed acetabular component with an alumina inlay (ABS Cup; Kyocera, Kyoto, Japan) (Fig. ), KC stem (Kyocera), and 28-mm alumina femoral head. Four patients (four hips) died within 27 months after the operation without complications from surgery. Two patients (two hips) were excluded because of recurrent dislocation and one patient (one hip) was excluded because of deep infection; these patients underwent revision surgery within 24 months. Three patients (three hips) were lost to followup. The remaining 67 patients (72 hips) were followed for a minimum of 5 years. There were 60 women and seven men. The mean age at the index operation was 63 years (range, 41–87 years), mean weight 53.9 kg (range, 38–85 kg), mean height 152 cm (range, 138–172 cm), and mean BMI 23.2 kg/m2 (range, 16.2–34.7 kg/m2). The primary diagnosis was osteoarthritis in 61 hips, osteonecrosis in five, rheumatoid arthritis in four, and sequelae of pyogenic infection in two. The minimum duration of followup was 5 years (mean, 6.7 years; range, 5–8.3 years) (Table ). The study was approved by the Institutional Review Board of the hospital, and all patients provided informed consent.
Fig. 1A–C A spherical cemented polyethylene-alumina composite cup, ABS cup (Kyocera, Kyoto, Japan), was developed to obtain stability between the alumina cup and bone cement. There were two designs for this cup: (A) one is the ABS cup without a flange and (B) (more ...)
Demographics of the 67 patients
The acetabular components consisted of a spherical cemented polyethylene socket with an alumina inlay (ABS; Kyocera) without a flange (Fig. A) in 20 hips and the same socket with a flange (Fig. B) in 52 hips. The outer diameter of the acetabular component was 42 mm in 14 hips, 44 mm in 42, 46 mm in eight, 48 mm in seven, and 50 mm in one. The femoral component was a tapered collarless titanium stem (KC stem; Kyocera). The stem was tapered only in the anteroposterior projection. The proximal end of the stem was coated with macrotexture. The neck-shaft angle of the stem was 130°. The standard offset was 40 mm in 42 hips, and the offset of the narrow stem was 35 mm in 30 hips. The femoral component was fixed with Simplex P® cement (Stryker Howmedica Osteonics, Allendale, NJ). A 28-mm alumina femoral head (Kyocera) was used. A short neck-head component was used in 18 hips, a medium neck in 50, and a long neck in four. All operations were performed by one surgeon (HO) through an anterolateral approach in which an attempt was made to place the acetabular component in an anatomic position.
All patients received intravenous antibiotic prophylaxis preoperatively and for 3 days after surgery. The patients received mechanical prophylaxis for thromboembolism by intermittent pneumatic compression with the A-V Impulse System® (Novamedix, Andover, UK) for 2 days, but no pharmacologic prophylaxis using warfarin, heparin, or aspirin was administered. Patients were encouraged to walk with full weightbearing as tolerated without the aid of crutches 4 weeks after surgery. Routine followups were scheduled for 3, 6, 9, and 12 months and yearly thereafter.
We (HI) performed clinical evaluation using the Merle d’Aubigné and Postel score [16
] that allocates up to 6 points for each category of pain, mobility, and function with a total of 18 points given to a normal hip. Patients were routinely asked at followup whether they had experienced audible hip noise because we were concerned about separation of alumina-on-alumina bearings and alumina fractures [18
The radiographic evaluation was performed by one observer (KI) who did not participate in the index operations. The 6-month anteroposterior and lateral radiographs were used for assessment of the abduction angle of the acetabular socket [17
]. On the radiographs at the final examination, radiolucency and osteolysis were evaluated around the acetabular component using the zone classification of DeLee and Charnley [9
] and around the femoral component using the criteria of Hodgkinson et al. [15
] and Gruen et al. [11
]. Migration of the acetabular and femoral component center was evaluated by comparing the horizontal and vertical distance from the inferior points of the teardrops and the center of the lesser trochanter, respectively, on the immediate postoperative and final radiographs [20
]. Loosening of each component was considered to have occurred when migration of the component was greater than 2 mm. Alumina component failure was checked. Heterotopic ossification was defined according to Brooker et al. [7
The mean Merle d’Aubigné and Postel hip score of the remaining 68 hips improved from 10.1 (pain 2.4, mobility 4.2, function 3.5) before the operation to 16.3 (pain 5.8, mobility 5.6, function 4.9) at final followup. No patient used any type of walking support. On 6-month anteroposterior radiographs of the 76 hips, the mean abduction angle of the acetabular component was 37.6° (range, 20°–50°). On the final radiographs of the remaining 68 hips, we found radiolucencies around the acetabular component in Zone 1 in 20 hips, in Zone 2 in five, and in Zone 3 in four. However, there was no osteolysis in any zone around the acetabular component and no evidence of migration of the acetabular component. On the femoral side, there was no radiolucency or osteolysis in any of the hips. No patients had heterotopic ossification. During the followup, there were no cases of nerve palsy, deep vein thrombosis, or pulmonary embolism.
Cumulative survival rates were calculated using the Kaplan-Meier method with failure defined as the end point of revision for alumina failure or for any reason. To compare groups with and without alumina failures in age, BMI, gender, mobility, function, abduction angle, size of component, or the existence of radiolucent lines, we used the nonparametric Mann-Whitney U-test. Fisher’s exact probability test was used to compare the alumina failure rate between polyethylene acetabular components with and without flanges. All analyses were performed with SAS® software (Version 9.1; SAS Institute Inc, Cary, NC).